In recent years, stacked image sensors have been proposed (e.g., see PTL 1).
The stacked image sensor is made up of a pixel array section, peripheral circuits, and a memory stacked one on top of the other.
The pixel array section is configured to perform photoelectric conversion and have multiple pixels arrayed therein to output a pixel signal each. The peripheral circuits perform various kinds of signal processing including analog-to-digital (AD) conversion of the pixel signals output from the pixel array section. The memory temporarily stores the result of AD conversion of the pixel signals.